Opioids are substances that derive from a natural chemical from the poppy plant, it relieves pain and induces sleep. Opioids have been used for centuries to treat cough, diarrhea, and pain. However, they also cause euphoria by activating reward regions and flooding the circuit with dopamine, which is the potential cause of addiction. Once in the system, opioids attach themselves to opioid receptor proteins (found on nerve cells in the spinal cord, gastrointestinal tract, and brain) and send signals to the brain which diminishes pain, and slows breathing.This drug can be found as an ingredient of a prescription drug or as an illegal one, in both cases, there are chances of becoming addicted and abusing the substance, this can cause a number of effects on the body if used long-term. Heroin or crushed-pill injections can cause veins to collapse, infections in the heart lining, slowing of the digestive system which can cause constipation, nausea and vomiting, major depression, sedation in the brain, immune system vulnerability and infection, respiratory depression, and if shared infected needles are used it can cause hepatitis. It is especially difficult to quit using opioids because they seize control of the neurotransmitters of the brain and withdrawal can cause depression, anxiety, lack of energy, and decreases the pain tolerance. A study done to determine some of the reasons why addicts fall into drugs such as opioids was done by Kendler, Jacobson, Prescott, & Neale. They wanted to examine shared and genetic-environmental risks for substance use disorders, using 1196 male-male twins from the Virginia Twin Registry they interviewed them personally and assessed their history on cannabis, cocaine, hallucinogens, sedatives, stimulants, and opiates dependence or usage. The results showed that environmental factors were key in determining whether the person would be a user or not. Genetic factors were also indicative of whether a person would become an abuser or not. This was true in all of the six classes of substances tested.